The Quantum Space Race

Posted by
Sam Churchill
on
March 5th, 2013

A quantum space race is under way to create the world’s first global quantum-communication network, reports Space Daily. Sending satellites equipped with quantum technologies into space will be the first step towards a global quantum-communication network says Thomas Jennewein and Brendon Higgins in this month’s Physics World.

The field of quantum communication – the science of transmitting quantum states from one place to another – has received significant attention in the last few years owing to the discovery of quantum cryptography.

Quantum cryptography exploits a unique property of single particles, such as photons: they can exist in two separate states – such as vertically polarized or horizontally polarized – or something in-between, known as a quantum superposition.

Upon measuring the state of a particle you instantly change this state, meaning an encryption key made of photons can be passed between two parties safe in the knowledge that if an eavesdropper intercepts it, this would be noticed.

Quantum cryptography has been described as a way of creating “unbreakable” messages and has attracted the attention of major technology companies, governments, banks and other security-focused clients.

The transmission of encryption keys over long distances still remains a significant challenge for scientists, however, as the intensity of signals tends to weaken as they travel further because photons get absorbed or scattered off molecules.

Up until now, the furthest that quantum-communication signals have been sent is a few hundred kilometres, which would realistically enable communication between just one or two cities.

A signal traveling from a ground station on Earth to a satellite would spend most of its time in the empty vacuum of space – rather than in Earth’s atmosphere, which is crowded with gas molecules – so the signal would travel a lot further without weakening.

A satellite orbiting at around 32000 km above Earth would act as a kind of relay between two ground stations in a way that allows them to establish a secure link by sharing an encryption key made of photons.

In addition to the basic mass and power of the satellite itself, the team led by Jennewein and Higgins has been studying the overall design features of the satellite and ground stations and has emphasized the need for them both to be precisely aligned so they can be certain that what they are measuring correctly corresponds to the photons that are prepared.

According to Thomas Jennewein and Brendon Higgins, the first step towards space-based quantum communication would be to place a satellite in a low-Earth orbit (LEO) – i.e. at an altitude of less than 2000 km. While a satellite in LEO can see only a small area of the Earth’s surface at once, its coverage includes all of the Earth at different, sometimes multiple, times in a single day.

Several research groups are pursuing the concept of a quantum satellite in friendly competition, say the researchers, including the National University of Singapore, which is preparing to launch a small “CubeSat” with an enclosed entangled photon source on board. MagiQ Research does contract research and development for optics, quantum information, fiber sensing, aerospace and defense applications and works with private firms and government agencies such as the Army, DARPA, and NASA.

Ball Aerospace is good at optical satellite components. Ball Aerospace has also launched Opticks, the company’s first open source software project. It enables detailed analysis of remote sensing data. Opticks is used by scientists and analysts within the Department of Defense Intelligence Community to analyze remote sensing data and produce actionable intelligence. Opticks supports Imagery, Motion Imagery, Synthetic Aperture Radar (SAR), and multi-spectral and hyper-spectral remote sensing data.

“Ball Aerospace’s Opticks demonstrates how government-sponsored code originally developed by a contractor can be maximized by releasing it as open source,” said John M. Weathersby, executive director of the Open-Source Software Institute.

“With the prospect of global-scale quantum communications and fundamental quantum science within new, unexplored regimes, the next few years are sure to be exciting,” say Jennewein and Higgins in Physics World.